The present invention relates to machines for repairing or reconditioning railroad rights-of-way and more specifically relates to a machine adapted to orient randomly stored rail tie plates in a specified length-to-width, top-to-bottom and high side-to-low side orientation and to transport the oriented plates for subsequent accurate placement thereof upon railroad ties.
Tie plates are used to secure rails to railroad ties and comprise a generally flat steel plate with a substantially flat bottom, a plurality of spike holes located side ends of the plate, and an upper surface having a pair of parallel, vertically projecting rail securing ribs or shoulders which define a rail seat therebetween. The tie plate upper surface is slightly angled to provide an inwardly canted rail seat, with more mass located on the field or "high" side of the plate to compensate for the force distribution of trains negotiating curves at high speed.
In the process of reconditioning railroad rights-of-way, the existing rail is removed along with the spikes and tie plates, the ties are replaced or resurfaced, and the track bed or ballast is refurbished. Before new rails are laid, replacement or recycled tie plates must be accurately positioned upon the ties.
Tie plate replacement is a cumbersome and labor-intensive operation, due to the significant weight of the individual plates (18-40 lbs. each) and the rapid rate at which they must be positioned to keep up with the other operations of track reconditioning, most of which are largely automated. Normally a member of a plate handling crew must retrieve steel plates individually from an often tangled pile and properly orient each plate for setting upon the upper surface of a tie to form new track beds. Two hands are required to position each plate due to their size and significant weight. If the plate is inverted, a worker must get his fingers under the plate and turn it over. Typically this is done on the ground or on a steel table often surrounded by other plates and track material. Accurate plate placement is critical, for the plates are required to be positioned within 1/4 inch on an imaginary x-y plane parallel to the ground. The configuration of the plates is such that the shoulders must be facing upwardly, the planar surface must be on the bottom, and the larger or "field side" located outwardly for proper said placement thereon. It has been estimated that a member of a plate feeding crew will handle 150,000 pounds per 8 hour shift. In order for the manual plate setting operation to keep up with the other automated track reconditioning operations of the rail gang, the workers must lay plates at 30 to 40 plates per minute for maximum rail gang efficiency. Considering the relatively rapid rates of placement required, as well as the degree of accuracy required, operator effort and safety become major concerns.
Previous attempts at automating the tie plate setting operation often resulted in devices largely concerned with the actual placement of the plates upon the ties. These prior art setters often depend on a supply of plates which had already been manually oriented, either on or off-site. On-site, plates are pre-positioned along the shoulder of the track bed, or carried in a gondola to be fed via conveyors to the plate setting device. One such prior art mechanism employs a magnetic pick up wheel and conveyor to transport plates from the tracks shoulder to a hopper, when they are manually oriented and placed on a crawler chain carrier for deposition upon the ties. Regardless of the apparatus employed, the rapid rate of 30 to 40 plates per minute at which conventional tie plate setters must operate to keep up with other automated track maintenance equipment requires extensive preplacement and labor intensive manual handling and sorting of plates. In addition, prior art devices are capable of setting plates for only one rail at a time.
Thus, there is a need for an automatic tie plate setting machine capable of accurately and automatically setting plates at 30 to 40 plates per minute with a minimum of manual handling and sorting.